Probably already been said. If so, delete or merge.
1. his ego can't take having qualified assistants, or
2. he can't recruit, or
3. qualified assistants don't want to work for him, or
4. all of the above, plus some
1. his ego can't take having qualified assistants, or
2. he can't recruit, or
3. qualified assistants don't want to work for him, or
4. all of the above, plus some